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Is This Patient REALLY Penicillin-Allergic? Try the PEN-FAST Decision Tool

July 19, 2023

Written by Andy Hogan

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PEN-FAST is a clinical decision-making tool that effectively identifies patients with self-reported penicillin allergy who are at negligible risk of hypersensitivity reaction after exposure to these antibiotics.

Don’t be too (PEN) FAST to skip the penicillins
Many first-line antibiotics for ED use are penicillin derivatives, and clinicians often avoid administering penicillin derivatives to patients who report penicillin allergy. Second-line antibiotics may have unfavorable adverse effects or increased risk of contributing to antibiotic resistance.

In the era of the electronic medical record, a “penicillin allergy” can easily sneak into a patient’s chart based only on a patient’s subjective report. The PEN-FAST tool (Figure 1) focuses on high-risk features of true hypersensitivity reactions to risk stratify patients reporting history of penicillin allergy. This retrospective observational study applied PEN-FAST to 120 outpatient allergy clinic patients who underwent penicillin skin testing or oral drug challenge. Of 88 patients that scored ≤2 on PEN-FAST, none experienced a true allergic reaction after receiving an observed oral dose of antibiotic, yielding a NPV of 100%. While the results are promising, all testing occurred in a controlled setting under allergist supervision.

How does this change my practice?
Distinguishing signs of hypersensitivity reactions (e.g., anaphylaxis, angioedema, severe cutaneous reaction) from less worrisome findings (e.g., nausea, itching, nonspecific rash, anxiety) might be more difficult for non-allergists in acute care settings. Nevertheless, PEN-FAST may help us determine which patients with reported penicillin allergy can safely receive these medications.

PEN-FAST Clinical Decision-Making Tool
From cited article, Figure 1. The PEN-FAST Clinical Decision-Making Tool (from the article’s Supplemental Online Content)

Evaluating the PEN-FAST Clinical Decision-making Tool to Enhance Penicillin Allergy Delabeling. JAMA Intern Med. 2023 Jun 20. doi: 10.1001/jamainternmed.2023.1572. Online ahead of print.

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